(1) Field of the Invention
The present invention pertains to a lubricant retention assembly employed with an electric motor that has a self-contained lubricant reservoir. More specifically, the present invention pertains to a thrust collar mounted on the motor shaft and a bearing cap surrounding the thrust collar, where the thrust collar has an annular flange that throws lubricant leaking along the shaft radially outwardly toward the bearing cap and the bearing cap has an angled interior surface that deflects the lubricant thrown by the annular flange into the motor interior and toward the lubricant reservoir. In addition, a thrust washer is provided on the shaft adjacent the thrust collar for preventing lubricant leakage along the shaft between the interface of the shaft and thrust collar. The thrust washer and thrust collar have complementary configurations that maintain the thrust washer in position on the shaft adjacent the thrust collar.
(2) Description of the Related Art
In most motor constructions having rotating drive shafts, proper lubrication of the drive shaft and the bearing surfaces or bearing assemblies supporting the shaft is essential for insuring a prolonged operating life and quiet operation of the motor. Some larger motors are constructed with their own lubrication circuits where a pump pumps lubricant from a reservoir to the shaft bearing assemblies and the lubricant is then directed back to the reservoir. The internal combustion motors of automobiles are examples of these types of motors. Any lubricant lost from the motor over time due to leakage past the bearing assemblies supporting the motor shaft can be replenished by supplying additional lubricant to the motor reservoir from a separate source. Because the lubricant can be replenished with periodic maintenance of the motor, the occasional loss of lubricant or loss of lubricant over time does not significantly detract from the operating life of the motor.
However, this is not the case with smaller motors, for example electric motors used in electric household appliances like dishwashers, clothes washers and clothes dryers. These types of motors are contained in the enclosures of the appliance and are inaccessible for replenishing lubricant lost due to leakage. The lubrication reservoir of these types of motors is self-contained and cannot be replenished. The motor shafts for small motor constructions are usually not supported for rotation by ball bearing or roller bearing assemblies, but by sleeve bearings or porous sintered metal bearings where bearing surfaces support the shafts for rotation. Loss of lubricant from these types of motors can cause the bearings to fail and can have serious consequences on the motor's operational life.
One of the major causes for sleeve bearing failures is loss of oil out of the bearing/lubrication system. An example of a conventional bearing/lubrication system used in appliance motor designs is shown in FIG. 1. The system shown in FIG. 1 is known in the prior art, and therefore only a partial view of the motor is shown.
FIG. 1 shows a porous powdered metal or babbitt metal type bearing (10) supporting the motor shaft (12) for rotation in an end shield (14) of the motor. The center axis A—A of the shaft (12) defines mutually perpendicular axial and radial directions. A cooling fan (16) is shown mounted on the shaft (12) to the right of the bearing assembly shown in FIG. 1. The interior of the motor is to the right of the end shield in FIG. 1. The shaft (12) extends through a cylindrical collar (18) of the motor end shield that surrounds the end shield shaft opening (20). The bearing (10) is held in the shaft opening (20) by its engagement with bearing seat surfaces (22) of the end shield on one side of the bearing and a bearing retainer (24) on the opposite side of the bearing. The typical bearing retainer (24) is constructed as a stamped metal disc (26) with a peripheral rim (28) that is press-fit into the end shield collar (18). A plurality of resilient fingers (30) project radially inwardly from the disk (26) and engage against the bearing (10) and hold the bearing to the bearing seat surfaces (22).
The typical bearing lubricant feeding and return system comprises a lubricating oil, felt or other fibrous material (32) injected with the oil, a thrust collar/oil slinger (34) and a bearing cap (36).
As seen in FIG. 1, the thrust collar/oil slinger (34) is mounted in a press-fit engagement on the shaft (12). A rubber washer (38) and a metal washer (40) are positioned between the collar (34) and the bearing (10). The engagement of the rubber washer (38) around the shaft provides a seal around the shaft surface that minimizes oil from leaking out of the motor interior along the interface between the shaft and the interior bore of the thrust collar (34). The metal washer (40) provides a sliding surface between the rubber washer (38) and the bearing (10) that prevents wear of the rubber washer on rotation of the shaft.
The bearing cap (36) is typically stamped from sheet metal and is formed with a resilient annular outer wall (42) that is press-fit into the end shield collar (18) surrounding the shaft opening (20). A cylindrical side wall (44) extends axially from the bearing cap outer wall (42) to a circular end wall (46) of the bearing cap. The bearing cap end wall (46) extends radially inwardly from the bearing cap side wall (44) toward the motor shaft (12) and terminates at an axially inwardly projecting lip (48) of the cap. The cap lip (48) is spaced radially outwardly from the fan (16) and shaft (12) leaving a clearance area (50) between the cap lip (48) and the fan (16) and shaft (12).
The area axially between the bearing retainer disk (26) and the bearing cap end wall (46) and radially outside the dashed line B—B shown in FIG. 1 is typically occupied by the lubricant-permeated fibrous material. This material is not shown in FIG. 1 to avoid obscuring other component parts of the bearing lubrication system.
In the intended operation of the prior art bearing lubrication system shown in FIG. 1, any lubricant advancing along the shaft (12) would be restricted from passing through the interface of the thrust collar/oil slinger (34) and the shaft by the rubber washer (38). The washer (38) is typically stretched as it is mounted on the shaft (12) and is in a tight engagement around the shaft, preventing any lubricant from advancing beyond the washer out of the motor. However, rotation of the shaft (12) also causes lubricant that is advanced along the shaft to move radially outwardly over the metal washer (40) and the thrust collar/oil slinger (34). Any lubricant that travels radially outwardly over the surfaces of the metal washer (40) is thrown from the peripheral edge of the metal washer into the fibrous material (32) that absorbs the lubricant. The material (32) wicks the lubricant back to the bearing (10). The lubricant soaks through the porous bearing to its center bore, re-lubricating the rotating engagement of the shaft (12) with the bearing (10). Any lubricant that travels radially outwardly along the rubber washer (38) is transferred to either the metal washer (40) or the thrust collar/oil slinger (34) which have greater radial dimensions than the rubber washer. Any lubricant that travels radially outwardly along the thrust collar/oil slinger (34) is thrown radially off of an annular rim (54) on the side of the thrust collar or off of the outer peripheral edge (56) of the thrust collar to the fibrous material (32). This lubricant is then wicked through the material (32) back to the porous bearing (10) that absorbs the lubricant and again transfers the lubricant to the rotating engagement of the shaft (12) with the bearing (10).
The bearing lubrication system described above and shown in FIG. 1 has been found to be disadvantaged in that lubricant thrown radially off the spinning thrust collar will at times impact against the interior surface of the fibrous material (32) represented by the dashed lines B—B and splash back onto the surface of the thrust collar (58) outside of or to the right of the thrust collar peripheral edge (56). When the motor is stopped or running, oil that has splashed onto the thrust collar outer surface (58) can advance along the surface of the fan hub (60) reaching the fan blades (62). The next time the motor is activated, the lubricant that reaches the fan hub (60) and fan blades (62) will fly off the blades, resulting in a loss of lubricant from the lubricant reservoir of the motor. In addition, when motors having a bearing lubrication system such as that shown in FIG. 1 are employed in a clothes dryer, lint can collect in the opening or clearance (50) between the bearing cap lip (48) and the fan (16) and soak up oil, causing additional loss of lubricant from the motor lubricant reservoir. Over time, the loss of oil can result in failing of the motor bearings requiring repair of the motor and the appliance.
What is needed to overcome the above shortcomings of the prior art bearing lubrication system is a system that reliably retains lubricant in the self-contained lubricant reservoir of an electric motor.